Method for varying the gradation of lenticulated color films



Sept. 24, 1940. w F T ET AL I 2,216,004

METHQD FOR VARYING THE GRADATION OF LENTICULATED COLOR FILMS Filed NOV.24, 1937 L NA |\b Second Sens/fv'zea laye r fiufi/JO/fT I q I Ema/5mm iE I g W In uehfors.

Patented Sept. g4, mo 2,216,004. v

mrrnon roa vsnrme m GRADA'I'ION or mm'icvmrnp COLOR. FILMS WolfgangFalta, Berlin, Edgar Gretener, Berlin- Siemensstadt, Hans Nengebauer,Berlin-Charlottenbllrs', nd Herbert Staude, Berlin-Tempel-'hoi.',-Germany, assignors, by mesne assignments, -to KislynCorporation, New York, N. Y., a corporation of Delaware ApplicationNovember 24, 1937, Serial no. 178,194 In Germany November 25, 19368Claims.

This invention relates to a method for varying the gradation oflenticulated color films.

The gradation or lenticulated films is a characteristic which determinesboth the contrast of with which the part colors corresponding to thepoint of the object are reproduced, this ratio should not be changed byany means if the gradation of the total picture is to be enhanced orlessened. This means that the resolving power the finished image and thecolor quality of images of the additional image must be somewhat of 5 tobe reproduced in colors which are produced the magnitude of the order ofa lentieular eleaccording to the lenticular color process. For a mentand that it should not be about three times proper reproduction of thecolors it is necessary greater, since otherwise besides the change inthat the photographic layer have an emulsion gradation as a whole also achange in gradation 10 whose gamma lies in the neighborhood of unity,affecting the reproduction of colors would occur. 10 whereas in the caseof smooth film the gradation The invention may be practiced in differentis always so chosen that the resulting gamma is ways, selected ones ofwhich will now be deconsiderably higher, for instance, of the orderscribed and which will be better understood by or 1.6 to 2. v referenceto the accompanying drawing, in which:

The selection of the resulting gradation when Fig. 1 is a diagrammaticview on a greatly en- 15 taking. pictures on films depends among otherlarged scale showing a cross-section through a things upon the selectionof the object. Thus portion of a lenticulated film and also showingparticularly in the case of big closeups a smaller certain curves orgraphs which will be referred gradation is employed than is usual forpictures to later;

which represent a greater number of objects Fig. 2 is a diagrammaticview on a greatly en- 20 (long shots). larged scale showing across-section oi a diiierent If images are to be produced onlenticulated form of film than appearing in Fig. 1 and illuscolor filmsand their impression corresponds subtrating a dififerent method.stantially to the gradations usual in smooth films, In both Figs. 1 and2it will be understood that 5 an emulsion must be employed in which therethe parts are not necessarily to scale or to prosultant gamma difiersconsiderably from unity. portion, since certain dimensions may be exag-However, if the best reproduction of color is to gerated for clearnessof illustration. be obtained the resultant gamma must lie, as farReferring first to Fig. 1, it will be seen that as possible, in theneighborhood of unity. It has this figure shows a lenticulated filmwhich has hitherto not been possible to fulfill both condibehind thesupport I and emulsion 2. The film 30 tions with the aid of a singleemulsion, so that was exposed in the known manner by the use oi. in thecase of the projection of lenticulated films a three band colored filterand developed a a omp omis ad to be ad pted tw n th cording to thereversal method. In this case the reproduction of color and the totalgradation. emulsion has a transparency which varies as According to theinvention the development shown, for instance, by the curve a. Under the35 and the printing up o he ompletion of th upper three lenticularelements i photographed picture is so e e that the gradation within anobject whose color corresponds substantially .very small zones of the lyer is r n from to the color of the central filter band. The transthatwhich holds good for relatively larger zones. parency of th emulsion is,therefore, greatest To s either Particular devflilopmg procbelow thecentral band of each lenticular ele- 4o esses are employed or theimages, if desired, by t, whereas the transparency of the bands the useof particular layers are intensified or allotted to the lateral bandshas 'a small value. reduced in such a manner that the adatmn The ratioof the transparencies of the three part over greater zones is differentfrom that in small hands under each lenticulated element deter zones Itis also Possible when Printing by means mines in this case the color ofthe point of the 45 of a particular printing arrangement to arrangeobject to Be reproduce that the gradation be influenced in the desiredIn the embodiment shown in Fig 1 an bj t manneris photographed under thelower lenticular ele- In the method according to the lQVentlon 1t 15ments, which object has no predominating color 550 essential that theefiect of the addltlonal change and will be reproduced theref r gray orwhite in gradation be limited to greater Zones than is The values of thetransparencies corresponding necessary for the reproduction of colors.Since t th th filter b nd ar th fo approxj the quality of color in thelenticulated color" mately equal (curve b). It is to be noted thatprocess depends upon the values of brightness in the case of whiteobjects a perfectly homogeneous variation of the transparency results 55only if no straight boundaries are present between the single filterbands in the objective for taking pictures and if the dimensions of thedevice for producing the lenticulation are also so chosen that nointerstices exist between the images of the colored filter in theemulsion. However, in the case of straight boundaries the transparencyvaries according to the curve I) as shown in Fig. 1.

Furthermore, the average values c and d of the transparencycorresponding to the single points of the object without considering thecolor are plotted in Fig. 1. Therefore, the transparency Tl will differfrom the transparency T2, the ratio of these two transparenciesindicating the diiierence in brightness between the corresponding pointsof the object. This ratio determines, however, at the same time thecontrast of the entire image so that this ratio must be variable withoutvarying simultaneously the values individually indicated by the curves aand b.

Consequently, a method according to the present invention consists intreating the film after the development. with a potassium blchromatesolution in the dark room and then exposing it to the light from theside on which the film is lenticulated. In this case a chromate image isadditionally produced in the emulsion, which image is bright at thepoints at which the film has a small transparency. This chromate imageis now converted into a swelling plastic by swelling the whole film inwater in the known manner. The film is then treated with a stainingsolution which is absorbed by the swollen points of the emulsion but isrepelled by the points of the emulsion which are not swollen. To thisend, for instance, pinatype yellow is employed. in this manner thenegative originally present as chromate image is converted into apositive image which presents, however, far less details than theoriginal blackening owing to the small resolving power of the gelatincapable of swelling. P'articularly, the image produced by coloringreproduces no longer the differences in brightness below each lenticularelement but only the total gradation of the image. This variation oftransparency t isindicated by the curve e. A similar method may bepracticed with the use of a suitable ferric salt.

If the original treated as above described is printed in the usualmanner, not only the variation of transparency. of the blackening butalso the variation of transparency of the colored picture is transmittedto the copy. Since the colored picture represents only diflerenceswithin ranges of the size of the lenticular elements, only the gradationas a. whole is increased in this manner, whereas the reproduction properof color is not influenced. By a suitable selection of the stainingsolution, particularly of the density or of the color thereof, the totalgradation may be influenced to a large extent.

It is to be noted that the variation of the gradation in the case of theabove-described treatment of the original does not remain fixed as suchbut when printing it may be modified within certain limits by employingcolored light instead of white light. If, for instance, the color of thelight coincides with the color with which the film has been treated, thevariation of the gradation will be only relatively small, whereas whenemploying a printing light whose natural color is a complementary colorto that of the dye a considerably stronger influence of the totalgradation will result.

The intensifying process just described utilized the capability ofswelling of the emulsion layer. In this case it must be taken intoconsideration that during the normal treatment of 'a reversal film bathsare, as a rule. employed which exert a hardening action on the gelatin.I1 such films are to be treated according to the novel method, thehardening must be eliminated. This may be accomplished in a known mannerby employing a potassium bromide solution and a subsequent washing ofthe film.

Furthermore, it is advantageous to increase the sensitivity of thebichromate process in the known manner by employing suitable sensitizersso as to accelerate the intensifying process. To this end, for instance,lanthanum chloride is suitable.

In the above described intensifying process the emulsion of the pictureis used as a support for the additional image which varies the gradationas a whole. In this manner difliculties arise which aggravate theexecution of the process or which render it entirely impossible, forinstance, if the hardening of the original picture cannot be annulled toa sumcient extent. The method according to the invention may, therefore,be carried out in such a manner that when the original is completed, anadditional layer is applied to the film, this layer serving as a supportfor the picture varying the gradation. If, forinstance, a gelatin layertreated with a chromate solution is employed, the image tobe intensifiedis iurther treated in exactly the same manner as is the case in theabove-described embodiment of the invention.

Also a silver halide gelatin emulsion may be employed as a layer to besubsequently applied, the grains of the emulsion having such a size thatthe resolving power suffices no longer to separate the rangescorresponding to the single part colors. In this case such an emulsionis rendered capable of being developed by exposing the film from theside on which the film is lenticulated, in which case the gradation ofthe image may be varied to a great extent by effecting the developmentin a corresponding manner. Particularly, it is possible to enhance thegradation of the total image by treating the additionally appliedemulsion according to the reversal process so that a positive image isproduced relatively to the original. However, it is also possible to useonly a negative process so that the gradation is reduced by the negativeimage present on the additional layer. Such a film provided with acoating is shown in Fig. 2. I denotes the support for the coating, 2 isthe emulsion proper and 3 the layer subsequently applied which variesthe gradation to a great extent. It is preferable to employ in thislayer an emulsion which presents as flat as possible a gamma, forinstance, about 0.3 to 0.4

A particularly preferred embodiment consists in the fact that whenphotographing or printing such scenes in which the gradation of theimage should be greater than that of the colors, a film is employedwhich already contains both layers 2 and 3, the layer 2 having a greaterresolving power and 3 a smaller.

In some films the emulsion is besides pro-' vided with a protectivelayer of gelatin which is to prevent the completed image from beingscratched and which has been applied particularly for the methodaccording to the invention. For such films it is preferable to efiectthe bichromate process in this protective layer so that the emulsionproper does not come into contact with the color. Furthermore, theadvantage is obtained in that the entire blackening available in theoriginal layer is employed for the formation of the additional image,whereas when the emulsion swells up an image is produced which isinfluenced by the distribution of the silver in differently deep layersof the emulsion. This means that those portions of the layer which liecloser to the support are only varied by the light which penetrated thesilver lying in front of the portions in the direction of the light.Since in the case of the reversal process the greater part of the silveris distributed over the outer side of the film, falsifications ofgradation may thereby occur within the image.

It is essential to the additional image which varies the gradation as awhole that the resolving power be smaller than that of the emulsionproper of the color film. To attain this small resolving power even ifthe emulsion presents a better resolving power per se, it isadvantageous to effect the additional exposure with a very greataperture. Since the photographic layer always tance is of the order of afilter component image itis possible to fade the structure of theoriginal image to such an extent by the light coming from differentdirections that only the gradation is transmitted as a whole.

Another method for carrying out the invention consists in employing twoseparate developing processes for the original or the printing film, oneof which processes creates a small silver grain and the other a coarsesilver grain. For instance, the film may be substantially developed withthe aid of paraphenylenediamine and then be subjected to a shortsubsequent development,

in the case of which, owing to the production of a coarse grain, acorresponding small resolving power is present.

-In general, it is advantageous to subject a film of which prints havebeen made to the method according to the invention in order to simplifythe method. If, however, for instance, only a few' prints are to obtainthe varied gradation, it is also advantageous to effect the printingprocess in such a manner that besides the recording corresponding to thecolors also an image is produced which substantially corresponds to thechange in gradation. This may be accomplished, for instance, byarranging behind the printing film a surface which directs the lightpassing through the film once more to the emulsion so that the zonescorresponding to the single component colors cannot be clearlydistinguished from one another. To this end, for instance, a slightlyroughened reflecting pressure plate in the film gate is sufiicient. Byvarying the reflecting power of this plate it is possible to obtain amore or less great change in gradation as a whole with a constantgradation in details.

We claimr 1. In color photography, the method which comprises forming animage of an object in the sensitized layer of a lenticulated film, saidimage comprising a group of color records behind each lenticulation, thesum of colors of the filters used to produce the records in each groupgiving substantially the efiect of white light, and then forming inregister on the image therein a supplementary duplicate image, theresolving power of which has a magnitude which is of the order of thatof one of said lenticulations.

2. In color photography, the method which comprises forming on an imagein the sensitized layer oi an exposed lenticulated film a supple mentaryduplicate image, the resolving power of which has a magnitude which isof the order of one lenticulatio'n.

3. In color photography, the method which comprises forming an image ofan object in the sensitized layer of a lenticulated film, said imagecomprising a plurality of groups of color records, the sum or .thecolors. or the filters used to produce the records in each group givingsubstantially the efiect of. white light,- treating the film with asensitizing agent which on exposure to light renders the resensitizedlayer differentially absorbent to dye solutions, exposing said image tolight through the film base, swelling the unexposed portions 01' theresensitized layer, and then treating with a staining solution of acharacter which will be differentially absorbed by the swollen parts ofthe sensitized layer,

4. In color photography, the method which comprises forming an image ofan object in the sensitized layer of a lenticulated film, said imagecomprising a plurality of groups 01' color records, the sum of thecolors of the filters used to produce the records in each group givingsubstantially the 'efi'ect of white light, treating said layer withchromic salts, exposing to light pass.- ing through the film base, andstaining'with a material which is diflerentially absorbed by parts oi!the layer swollen by said salts.

5. In color photography, the method which comprises forming an image ofan object in the sensitized layer of a lenticulated film, said imagecomprising a plurality of groups of .color records, the sum of thecolors or the filters used to produce the records in each groupv givingsubstantially the efl'ect of white light, treating saidi layer withpotassium bichromate, exposing to light passing through the film base,and staining with a material which is diflerentially absorbed by partsof the layer swollen by said p0- tassiurn bichromate.

6. In color photography, the method which comprises forming an image ofan object in the sensitized layer of a lenticulated film, said imagecomprising a plurality of groups of color records, the sum of the colorsof the filters used to produce the records in each group giving substantially the eflect of white light, then forming on the image thereina supplementary duplicate image, the resolving power of which has amagnitude which is of the order of a lenticulation, and printing fromsaid film with colored light.

'I. In color photography, the method which comprises forming an image ofan object in the sensitized layer of a lenticulated film, said imagecomprising a plurality of groups of color records, the sum of the colorsof the filters used to produce the records in each group givingsubstantially the eflect of white light, treating the mm with asensitizing agent which on exposure to light renders the resensitizedlayer difierentially absorbent to dye solutions, exposing said image tolight through the film base and through a lens having a relatively largeaperture, swelling the unexposed portions of the resensitized layer, andthen treating with a staining solution of a character which will bedifferentially rial which is differentially absorbedby parts of thelayer swollen by said salts.

' WOLFGANG FALTA.

EDGAR GRETENER. HANS NEUGEBAUER. BIB-BERT BTAUDE.

